Withdrawal head for continuous-casting moulds and method of using same



Aug. 25, 1970 LEESE ET AL 3,525,381

WITHDRAWAL HEAD FOR CONTINUOUS-CASTING MOULDS AND METHOD OF USING SAMEFiled March 25, 1968 DJ R\\' 1\ x7 INVENTORS FREDERICKJ. LEESE WILLIAMH. SUMMERS "Maw ATTORNEYS United States Patent 3,525,381 WITHDRAWAL HEADFOR CONTINUOUS-CAST- ING MOULDS AND METHOD OF USING SAME Frederick JohnLeese, Stoke-on-Trent, and William H.

Summers, Hampton Hall, near Malpas, England, assignors to Concast AG,Zurich, Switzerland Filed Mar. 25, 1968, Ser. No. 715,694 Claimspriority, apppl-icgtigiari/fgwitzerland, Apr. 6, 1967,

Int. (:13 B22d 11/08 US. Cl. 164-82 14 Claims ABSTRACT OF THE DISCLOSUREThe invention relates to the continuous casting of metals, particularlysteel, by pouring liquid metal into a cooled open-ended mould andwithdrawing the casting, when this has formed a solidified skin, bymeans of a dummy casting attached to a withdrawing head.

In a continuous-casting plant comprising an openended mould it is knownto close the bottom end of the mould by a dummy casting attached to awithdrawing head before casting begins. The stopper thus formed retainsthe infiowing liquid metal until the mould has been filled, when thecasting formed can be continuously withdrawn from the mould by startingup a set of withdrawing rollers.

From transmitting the pull during withdrawal it has been proposed toprovide a mushroom-shaped withdrawing head. In order to facilitate thesubsequent separation of the head from the solidified casting,refractory plates are inserted which divide the mould interior to thetop of the withdrawing head into two cavities. Moreover, the withdrawinghead is provided with a coating to prevent the metal from welding ontothe head. Although the area of such a withdrawing head is arranged toexceed half the cross-sectional area of the mould, it is stillimpossible to prevent the creation of major gaps between the roundwithdrawing head and the sides of the mould. Apart from the lengthy timeit takes for the steel to freeze in these large cavities, the momentsthat are applied to the metal that has solidified above the withdrawinghead in the hottest and therefore weakest zone in the casting crosssection is a drawback which frequently leads to a premature break-awayof the withdrawing head from the solidifying casting. Moreover, despitethe presence of the coating, the metal cannot be prevented from weldingonto the withdrawing head. Moreover, the base of the withdrawing headmust be protected from the liquid metal by a covering of chips. As amatter of experience these chips do not fuse completely and they thenscore and scratch the mould walls and any following cooling plates thatmay be provided.

It is therefore an object of the present invention to eliminate theabove described difliculties by providing a method of positivelycoupling the continuous casting to the dummy by means of a withdrawinghead which can subsequently be easily detached from the casting andwhich is so contrived that the continuous casting will not be stressedby the withdrawing pull at points where this is undesirable.

Patented Aug. 25, 1970 ice The invention therefore proposes a method aswell as apparatus which permit the casting to be satisfactorilywithdrawn from the mould and detached from the withdrawing head. Theproposed method consists in providing a withdrawing head having thegeneral form of a truncated pyramid with recesses formed in oppositesides and a base substantially filling the entire cross section of themould, thereby to form a cavity which tapers between the wall of themould and the withdrawing head towards the dummy casting, in sealingthis cavity to prevent metal from penetrating to the dummy casting, andin abstracting through the walls of the cavity sufiicient heat from thecast metal to establish coupling engagement with the withdrawing headwithout forming a weld, in such manner that the pull of withdrawal istransmitted substantially in the axial direction of the casting throughthe outer solidified skin without applying undesirable bending loads tothe solidifying metal.

The preferred form of withdrawing head is a truncated pyramid having abase and four sides inclined at an angle towards the casting axis, thebase is slightly smaller than the cross section of the casting, and atransverse recess is formed in each of two opposite sides.

In order that the invention may be more readily understood an embodimentand other features thereof will be hereunder described, by way ofexample, reference being made to the accompanying drawing, in which:

FIG. 1 is a sectional view of the bottom end of a continuous castingmould containing an inserted dummy casting,

FIG. 2 is a sectional view of the withdrawing head of the dummy casting,taken on the line IIII in FIG. 1, and

FIG. 3 is an elevation of the withdrawing head and the surrounding metalafter having been cut off the casting and detached from the dummy.

A withdrawing head 2 having transverse recesses 3 in two opposite sides6 is inserted into a mould 1 of rectangular cross section. For castingcross sections with unequal sides the two recesses should preferablyextend across the longer sides. The underside of the withdrawing head 2is attached to a dummy casting 4, for instance by means of a T-shapedanchoring pin 5 adapted to provide a push-and-turn coupling. The twosides 6, as well as the remaining two sides 9 of the withdrawing head 2,are inclined towards the casting axis. The withdrawing head, having anupper flat surface 8, thus has the overall shape of a truncated pyramid.The size of the base is so chosen that it substantially fills the crosssection of the mould. A sealing material 10, such as asbestos, is packedbetween the mould wall and the base of the withdrawing head 2 to form atight joint. Owing to the downwardly diminishing width of the gapbetween the wall and the sides of the head this joint effectivelyprevents the liquid metal, e.g. steel, from penetrating downwards to thedummy casting. The described configuration of the withdrawing headcreates spaces 12, between the mould wall and the sides 6 of theWithdrawing head, which narrow in the direction down towards the base 13of the withdrawing head; in this narrowing space the quenching elfect ofthe mould wall and the withdrawing head rapidly abstracts heat from thepoured metal so as to prevent the withdrawing head from being fused andwelding to the metal of the casting. Nevertheless, the liquid andrapidly solidifying metal which fills the lateral transverse recesses 3in the withdrawing head creates a positive coupling connection,permitting the withdrawing pull to be reliably transmitted to thecasting. The forces which are engendered during the process ofwithdrawal are transmitted by this coupling connection in such a waythat downward pulling force applies substantially in the axial directionof the casting through the surface layer which has already solidified,so that no major bending moments, are applied to the hot solidifiedmetal layer, which, above the top of the withdrawing head, still lacksmechanical cohesion and strength.

The continuous casting that is withdrawn from the mould-by withdrawingrollers-is separated from the withdrawing head 2 by a suitable cuttingtool (not shown) which cuts it off directly above the withdrawing head,for example, at a distance of 1 to 2 ems. therefrom. The withdrawinghead can then be removed from the dummy casting 4 by releasing thecoupling pin 5.

It will be understood from FIG. 3 that the metal 11 enclosing thewithdrawing head 2 can be divided into two halves by two substantiallyvertical cuts, as indicated at 15. The two pieces can then be pulledaway from the recesses to free the withdrawing head from the surroundingmetal without damaging the withdrawing head, which thus can be reusedrepeatedly. The economy of the process can be even further improved byusing the undamaged withdrawing head repeatedly without detaching itfrom the dummy. The time needed for preparatory work preceding a castingoperation can thus be reduced to less than 3 minutes. This afiords aconsiderable saving in time compared with conventional methods.

For casting steel, the withdrawing head is preferably made of cast iron.It has also been found that for achieving satisfactory results the angle7 which each side makes with the base should preferably be about 70. Theheight of the withdrawing head should not be less than 100 mm. to ensurea sufiiciently rapid withdrawal of heat. Furthermore, the distance of 14of the base 13 from the mould walls should be as small as possible andpreferably less than mm., since this facilitates the creation of a tightseal.

Its rapid solidification prevents the molten metal from welding to thewithdrawing head, thus permitting the latter to be reused after it hasbeen extracted from the surrounding metal. Since cooling chips need notbe packed around the withdrawing head the risk of scoring the wall ofthe mould is also eliminated. Experience has shown that a withdrawinghead can thus be used for about 10 castings in the continuous casting ofsteel. By covering the upper surface 8 of the head with a plate beforethe steel is poured into the mould, the life of the head can be extendedto more than castings. Conveniently, such a covering plate may consistof a material of the same quality as that which is to be cast.

What We claim is:

1. A method of continuously casting metals, comprising closing the openend of a cooled, open-ended permanent mould by a withdrawing head havinga dummy casting attached thereto, the withdrawing head having thegeneral form of a truncated pyramid with recesses formed in oppositesides and a base substantially filling the entire cross section of themould, said withdrawing head thus forming a cavity which tapers betweenthe mould wall and the withdrawing head towards the dummy casting,sealing said cavity to prevent liquid metal from penetrating to thedummy casting, pouring liquid metal into the mould and abstractingsufiicient heat from the cast metal between the walls of the cavity toestablish coupling engagement with the withdrawing head without theformation of a welded bend, and withdrawing the resultant continuouscasting, when this has formed a solidified skin, by means of the dummycasting whereby the pull of withdrawal is transmitted substantially inthe axial direction of the casting through the outer solidified skinwithout applying undesirable bending loads to the solidifying metal.

2. A method according to claim 1, further comprising cutting theresultant continuous casting adjacent the withdrawing head andsubsequently separating the metal enveloping the head into two parts andpulling them away from the recessed sides of the withdrawing head.

3. A method according to claim 1, comprising placing a cover plate overthe top of the withdrawing head before pouring the metal into the mould.

4. A method according to claim 1, comprising reusing the withdrawinghead for a subsequent casting operation without detaching it from thedummy casting.

5. A method according to claim 1 for casting steel, wherein awithdrawing head consisting of cast iron is used.

6. A method according to claim 1, wherein the gap between the base andthe mould wall is 10 mm. or less.

7. A withdrawing head for continuous casting apparatus comprising anopen-ended mould of rectangular cross section, said withdrawing headcomprising a truncated pyramid having a base and four sides which areinclined towards the casting axis, the base being only slightly smallerthan the cross section of the continuous casting, and transverserecesses being formed in opposite side faces.

8. A withdrawing head according to claim 7, wherein a said recess isformed in each of two opposite sides.

9. A withdrawing head according to claim 7 having a height of at least100 mm.

10. A withdrawing head according to claim 7 which, for use in thecasting of steel, consists of cast iron.

11. A withdrawing head according to claim 7, wherein the angle that thefour sides make with the base is about 12. A withdrawing head accordingto claim 7, comprising two longer and two shorter sides wherein therecesses are formed in the two longer sides.

13. A withdrawing head according to claim 7 in combination with a mouldwherein the base is dimensioned so that the gap between it and the mouldwall is 10 mm. or less.

14. A withdrawing head according to claim 7 comprising means forreleasably coupling to a dummy casting.

References Cited UNITED STATES PATENTS 3,262,161 7/1966 Andrzejak et al.164-274 3,266,104 8/1966 Foldessy et al. l64274 3,409,071 11/1968Ciochetto l64274 I. SPENCER OVERHOLSER, Primary Examiner I. E. ROETHEL,Assistant Examiner f US. Cl. X.R. 164-274, 282 i i

